Known are double-walled insulating dishes for storing and handling hot or cold foods and beverages to maintain their temperature at a constant level over an extended period of time. Great Britain Patent Publication No. 22447234A is exemplary. It discloses a food and drink container composed of an inner vessel and an insulated outer shell with a compartment there between containing a phase change material. The inner vessel is composed of stainless steel, aluminum or copper and the insulating material of the outer shell is an expanded polyurethane, polyethylene, polystyrene, aerogel or open or closed cell foam. The phase change material is a crystalline salt and a wax, fatty acid, fat, heavy alcohol or crystalline alkyl hydrocarbon. A lid is made of the same materials. U.S. Pat. No. 5,052,369 similarly discloses a heat maintaining food container composed of a body and a lid, each of which is formed with a compartment containing an insulating layer and a heat storing material. The insulating layer is closed cell foam such as Ensolite®, or preferably foamed polyurethane. The heat storing material is a paraffin base or micro crystalline wax.
Insulating layers other than waxes and the like are also known. U.S. Pat. No. 5,390,797 discloses a heat maintaining food storage container have a base and a hinged lid, both of which have a non-removable insulating liner composed of a closed cell foam rubber or closed cell foamed plastic. U.S. Pat. No. 6,668,577 discloses an insulated container for maintaining cold contents composed of a polypropylene case, a polystyrene insulating lining, a diffuser cover that includes an independent refrigeration source, a receptacle to hold the refrigeration source and an aluminum thermal bridge to assist in uniform distribution of the refrigeration. The diffuser cover and receptacle are formed from a single board of deformable thermal insulating material such as honeycombed polypropylene. POT Patent Application EP2011/073806, published as WO2012/085212, discloses a wall construction for thermally insulated containers for mobile catering. The container is made of inner and outer walls composed of a thermoplastic polymer. On the inner wall is a film formed from a thermoplastic polymer or polymeric foam having rib like stiffening projections. Between the film and the outer wall may be a vacuum insulation foam plastic honeycombed layer or panel. Disclosed materials to be used in the construction of the inner layer polyester or polyethylene variants such as LLDPE and metalized polyphenylene sulfide (PPS), polyethertherketone (PEEK), polysulfone (PSU), polyphynylene sulfone (PPSU), polyether (PES/PESU), polyetherimide (PEI), liquid crystal polymer (LCP) or styrene. The vacuum insulation panel may include an aerogel. The inner and outer walls are glued or welded together to form a single, solid unit.
U.S. Pat. No. 4,478,349 discloses a double-walled heating vessel including a lid, an outer container, and a removable inner container with a flange that allows it to set within the outer container, leaving an air space between the two. The components are made of polysulfone plastic (Udel®, Union Carbide) and U.S. Pat. No. 4,225,052 discloses a covered serving dish having an outer wall and an inner wall, both of which are formed of high-impact polyethylene or polystyrene. Between the two walls is a layer of insulating material such as expanded polystyrene or polyurethane. The serving dish cover is formed in the same way. Both disclosures appear pertinent to maintaining hot foods.
The abstract of Netherlands Patent Application Publication No. 1019227 discloses a refrigerated food serving system comprising a first box that can be sealed by placing a second box on top of it. A cooling element is disposed within the first box and sits on spacer elements or ribs in the base of the box, and a food dish is placed on top of the cooling element. The base of the first box is composed of a thermal insulation material and the side walls are made from a porous or breathable material. An air gap between the side walls and the food dish allows air circulation. Australia Patent Application Publication No. 86 500/82 discloses an insulated serving dish having a hinged lid for maintaining hot foods. The dish and the lid are composed of an external shell and an internal shell and between the shells is a heat insulating material such as polystyrol foam. A removable glass bowl contains the food and the external shell is provided with a peripheral rim that cooperates with an outwardly bent flange extension of the lid to form a bendable hinge.
As can be seen from the foregoing, there are a variety of insulators and food receptacle constructions that are already known it the art. Some maintain the cold temperature of the contents but cannot be used with hot contents and others maintain the hot temperature of the contents and cannot be used with cold contents. Others can be used for either hot or cold foods, but only if the construction and materials are modified. (See for example, POT Patent Publication WO20121085212,)
It would be advantageous to have to a food container that has the ability to insulate both hot and cold foods or beverages without modification to the structure or components of the structure. Such a dual purpose hot or cold insulating food service assembly is provided by the invention.